<!DOCTYPE html>
<html lang="zh_CN">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body{
            font-size: 13px;
        }
        .box{
            font-size: 12px;
            width: 100em;
            height: 100em;
            background-color: #f00;
        }
    </style>
</head>
<body>
    <div class="box"></div>
</body>
<script type="text/javascript">

</script>

</html>
